Primates Exam 3
3. For body size: insectivores < frugivores < folivores
- BMR: smaller animals require small but high-quality foods that can be processed quickly (e.g. insects), - Larger animals are less constrained by the quality of their food than by the quantity of food
Support for Frugivory Hypothesis
- Degree of frugivory vs. neocortex ratio - Home range size vs. neocortex ratio
Dominant males
- Dominant males have higher fighting ability - Dominant males may therefore be of higher quality than lower ranking males - Dominant males are also better at defending infants - If the dominant male drops in rank, females no longer prefer to mate with him -Recently deposed adult males are suddenly no longer attractive to females. Their genes haven't changed, only their rank
2. Primates rely more heavily on some types of foods than on others
- E.g., chimpanzees eat mostly ripe fruit; aye-ayes eat mostly grubs - Different dietary categories (folivores, frugivores, insectivores, etc.) refer to the primary foods
Alternative hypotheses for male infanticide
- Eliminate genes of current sexual rivals - Eliminate future sexual rivals - By-product of adaptive aggression - Social pathology - Cannibalism - Reduce resource competition • These have limited support
Female strategies: summary
- Female reproduction is limited by access to food - Because of slow reproductive rates, not only food, but also infant survival has a large impact on female reproductive success - Females therefore have a variety of strategies aimed at increasing access to food, safety, and high-quality mates
Active solicitation
- Females in estrus may follow a male around and sexually present to him - E.g. capuchin females make vocalizations, facial expressions, and even throw rocks - Black-and-white colobus females yank the male's penis
Confuse paternity
- Females may mate promiscuously to confuse paternity - Decrease infanticide risk - Increase number of males that provide infant protection
Amenorrhea
- Females may stop cycling (experience amenorrhea) when they have excessively low body fat - Fat reserves support embryo/fetus during gestation and milk production when the infant is nursing -Also true in humans: women with eating disorders, women in concentration camps ("war amenorrhea"), high performance athletes ("athletic amenorrhea")
New/unfamiliar males
- Females often prefer to mate with new immigrant males - Natal males are usually non-preferred partners - This preference may be an effective way to avoid inbreeding - Example: In rhesus macaques, females preferred to mate with new males (who are low-ranking) rather than the old dominant male
Mates with compatible genes
- Females should prefer males with compatible genes that will increase offspring fitness - Major Histocompatibility Complex (MHC) is a critical part of the immune system (Box 4.1) - More diverse MHC may be able to recognize a broader range of pathogens - MHC types can be assessed via olfactory cues - Some female primates prefer mates with different MHC - Females should prefer males with compatible genes that will increase the offspring's fitness by decreasing inbreeding risk and increase the infant's genetic variation which increases adaptability to changing environmental conditions - Fitness is largely affected by immunocompetence - Obtaining genetic constitutions for their offspring which provide them with superior immunocompetence immunocompetence is directly related MHC diversity
Males with good genes
- Females should prefer males with good genes that will increase offspring fitness (health, strength etc.) - Good genes are sometimes reflected by sexual ornaments (for example, face/rump color in mandrils) - Females may also assess a male's genetic quality based on their display behaviors or their vocalizations
Sexual swellings
- Form of indirect mate choice - Sexual swellings may increase male-male competition during peak estrus to ensure that females mate with the highest quality male during this time - Because mate guarding is costly, females get the opportunity to mate with other males during non-peak swelling stages - Sexual swellings do not lead to mate choice of a specific partner but merely increase male-male competition
Form strong relationships with adult males
- In several species, males are better protectors than females because of their larger size - Males often the most active during encounters with predators and extra-group males
Control group membership
- In some species, females may try to create a safe environment by controlling group membership - E.g. Ring-tailed lemurs - mothers attack new immigrant males - Females resist female immigration in several species
Refusal to mate
- In species with low sexual size dimorphism, females can refuse to mate with a male - E.g. vervet females reject half of males
6. Captive breeding and reintroduction
- In theory: • Restore or augment small wild populations from captive stock - Drawbacks: • Lack of suitable habitat and adequate protection • Can be very costly • Most captive bred animals can never acquire the skills they need to survive in the wild • Many linger around release site or attempt to return to breeding centre
Decrease risk of negative infant handling
- Infant handling can also decrease infant survival - E.g. baboons females "kidnap" infants - Avoid approaching high-ranking females - Form strong relationships with other group members to reduce the risk of negative infant handling
Support for Innovation Hypothesis
- Innovation frequency vs. neocortex ratio - Social learning frequency vs. neocortex ratio
1. Social factors that favor large brains: The Social Intelligence Hypothesis
- Intelligence and large brains are the results of selection favoring individuals who can successfully navigate this complex social world - Expansion of brain parts involved in learning, planning, and behavioral flexibility
Testes size relative to body size
- Larger testes produce greater quantities of sperm and may produce more motile sperm (i.e., that can move faster) - Testes are largest in species where females mate with several males - Testes are smallest in species where females mate with only one male
Penile anatomical adaptations
- Many primates have penile spines - These may shorten the duration of female sexual receptivity and reduce remating by females - Can also break through copulatory plugs - May act as plungers to displace previous sperm
Adulthood
- More or less continuous from puberty to death - No major stages or categories within the adult life course
Juvenescence
- Period from weaning to sexual maturity - Unlike infants, juveniles are likely to survive death of mother
What strategies do female primates use to create a safe environment for raising young?
- Protection from predators - Protection from conspecifics 1. Compete for safe spatial position in group 2. Form strong relationships with other females 3. Form strong relationships with adult males 4. Confuse paternity 5. Communal infant care 6. Decrease risk of negative infant handling 7. Control group membership
Behavioral adaptations to sperm competition
- Removing another male's sperm or copulatory plug before mating - Mate guarding to prevent sperm or copulatory plug removal - "Last male precedence": the last male to mate with a female is more likely to fertilize her egg because his sperm may displace or wash away other males' sperm
What strategies do males use to gain access to females for mating opportunities?
- Search for, acquire, and defend females or home ranges - Form social relationships with other group members - Male relationships with infants - Gaining mating access when females are most fertile - Sperm competition
4 components of communication
- Signal - Motivation - Function - Mechanism
1. Most primates rely on one food type high in protein (P) and one type that is high in carbohydrates (CH)
- Strepsirrhines: insects (P) and gum/fruit (CH) - Monkeys/Apes: insects/young leaves (P) and fruit (CH)
Compete for safe spatial position in group
- The spatial position in a group affects predation risk - The center of the group is safer than the periphery - High-ranking females are often in the center of the group - Low-ranking females are often at the periphery -May be chased out by high-ranking females
folivery
- Young leaves • Easier to digest, more proteins and sugars • Scarce - Mature leaves • High cellulose content, often have secondary compounds, require digestive adaptations • Abundant
What strategies do female primates use to choose with high-quality mates?
- dominant males - new/unfamiliar males - males with good genes - mates with compatible genes
Birth and Infancy: Artricial
- haplorhines - underdeveloped - physically helpless at birth - tarisers, monkeys, apes and humans
Birth and Infancy: Precoprial
- strepsirhines - well-developed - active or physically mobile at birth - lemurs and lorises
Mate choice via dispersal
-In species with female dispersal, females can transfer from a group with a low-quality male to a group with a high-quality male -E.g. male gorilla displays
Use of space
-day range -home range -territory
Females' requirements for successful reproduction
1) Food 2) Safety 3) High-quality mates -Increase her own and her offspring's survival -Provide infant protection and produce high-quality offspring -Because females invest more in each offspring, they have more to loose by choosing poor quality mates
Evidence that access to food and physical condition determine female reproductive rates
1. Greater fecundity (reproductive rate) in provisioned colonies 2. Amenorrhea
2 strategies to surviving the juvenile period
1. Grow quickly (used by strepsirrhines) 2. Grow slowly (used by haplorrhines)
Forms of male sexual coercion
1. Infanticide 2. Harassment 3. Intimidation 4. Mate guarding 5. Mate herding 6. Forced copulation
Major anthropogenic causes of habitat disturbance
1. Logging 2. Agriculture 3. Fires 4. Pollution 5. Climate change
Primate Diets: Generalizations
1. Most primates rely on one food type high in protein (P) and one type that is high in carbohydrates (CH) 2. Primates rely more heavily on some types of foods than on others 3. For body size: insectivores < frugivores < folivores
Infant socializing agents
1. Mothers 2. Adult males 3. Alloparents 4. Peers
Three characteristics of foods that affect foraging
1. Nutritional quality of food 2. Spatial distribution of food 3. Temporal availability of food
Strategies to protect primates
1. Protected areas 2. Sustainable use of natural resources 3. Integrated conservation and development projects 4. Community-based conservation 5. Ecotourism 6. Captive breeding and reintroduction 7. Education programs 8. Research
Male strategies to gain high reproductive success
1. Search for, acquire, and defend females or home ranges 2. Form social relationships that may lead to mating opportunities 3. Focus efforts to gain mating access when females are most fertile (i.e., during the estrus period)
Mechanisms of sperm competition
1. Testes size relative to body size 2. Copulatory plugs 3. Penile anatomical adaptations 4. Behavioral adaptations to sperm competition
Is it really deception?
Deception requires intentionally manipulating other's beliefs about the world, and an understanding of what the other is thinking • Hard to know if there is understanding • Hard to know if it's intentional • Example: false predator alarm calls in forktailed drones - This could be deception, or there could be a simpler explanation - Maybe they're paying attention to their targets, and they change what they're doing based on the feedback they receive
Infant mortality
Disease Stochastic events Infanticide
Why are these requirements for females in particular?
Female reproduction has high nutritional demands -Differential parental investment
Support for Social Intelligence Hypothesis
Group size vs. neocortex ratio
Anthropogenic threats to primates
Human population growth creates pressures that threaten primate populations: 1. Habitat disturbance 2. Hunting 3. Disease
Energetics of body size
Kay's Threshold: body weight that separates primarily insectivorous from non-insectivorous primates - Around 500 g - Small primates - Can ingest enough insects - Large primates - Low BMR = can tolerate longer lags between feeding bouts - Longer guts = can digest leaves
Nutritional Requirements
Macro and micronutrients
An arms race in reproductive strategies
Male and female reproductive strategies are often in conflict
Diet reflected in morphology
Primate diets can be reflected in tooth and gut morphology; useful for inferences from the fossil record
Conservation
Protecting species, their habitats, and ecosystems from extinction
Macronutrients
Proteins, fats, and carbohydrates that provide the bulk of an organism's metabolic requirements - Protein/amino acids for growth, reproduction, regulation of bodily functions - Mammals cannot synthesize many amino acids themselves, and therefore must obtain them from foods - Fats, oils, & carbohydrates provide energy
Infant mortality: Infanticide
The link with lactation time: • Lactation Time / Gestation Time • Females with long lactation periods tend to undergo postpartum amenorrhea + no post-partum mating occurs • After loss of infant, female resumes estrus sooner
Puberty
The process of sexual maturation • Hormonal changes induce physiological, morphological, and behavioral changes - In males, the testes begin producing testosterone - In females, the ovaries begin producing progesterone and estrogen • These changes stimulate the development of secondary sexual characteristics
Intimidation (male)
aggression toward receptive females that may make them more likely to mate with that male in the future rather than with other males
Harassment (male)
continually directing sexual solicitations, following, and directing aggression toward females that are reluctant to mate
Mate herding
controlling female movements to keep her away from other groups or males
Forced copulation
forcing the female to mate when she is unwilling
Endemism
found only in a particular region and nowhere else on Earth
frugivory
fruit
Insectivory
insects
Background extinction rate
natural extinctions • For mammal or marine species: each year 1 species out of every 1-10 million goes extinct
Life history: variation
reflects different strategies of allocating resources (e.g., time, effort, and energy) to competing life functions • Biological trade-offs - Quantity vs. quality of offspring - Current vs. future reproduction • Energy allocation - Growth - Maintenance - Reproduction
Copulatory plugs
secretions that harden to plug or glue the female female reproductive tract together - Prevents sperm leakage - Forms a barrier to subsequent copulations (although the plugs can be removed)
Mate guarding
staying in proximity to the female and aggressively keeping other males away from her (most effective against lower ranking males) - ex. gorillas
Day range
the area (or linear distance) used by an individual/group during a single day
Territory
the area that an individual/group defends; not equivalent to the home range!
Home range
the area used by an animal (or group of animals) in its normal activities of feeding, sleeping, resting, etc.
Extirpation
the disappearance of a population from a given area, but not the entire species globally
Infanticide
the killing of infants by males - Major cause of infant death in many primate species! • Sexual selection hypothesis for infanticide (requires these conditions to be true): - Male kills unweaned infants - Male is not the sire of the infant - Elimination of the infant shortens the inter-birth interval of the mother - Infanticidal male will gain increased reproductive access to the mother • Male increases his own chances of siring the female's next infant and the likelihood that this infant will survive
Life History Theory
the timing of key events in the organism's life have been shaped by natural selection to maximize the number of surviving offspring - Stages of juvenile development - Sexual maturity - First reproduction - Number of offspring and degree of parental investment - Senescence (i.e., becoming "old") - Death
Micronutrients
trace vitamins & minerals that are important for specific physiological functions
Extinction
when the last member of a species dies and the species ceases to exist
Primates understand third-party kinship
• "Third-party": not self or an individual you are directly interacting with • Experiment 1: Juvenile distress calls • Mother responds (knows kin) • Other females look at mother (know relationships of non-kin)
Foundation species
• A dominant primary producer in an ecosystem both in terms of abundance and influence • Examples: corals in coral reefs; kelp in kelp forests
The Sixth Mass Extinction
• A sixth mass extinction is underway (also called the "Holocene extinction" or sometimes the "Anthropocene extinction" • Holocene: begins ~12,000 years ago • Anthropocene: proposed geological epoch; begins either 1610 or 1964* • Worldwide extinction of megafauna (mammoths, saber-toothed cats, giant sloths, etc.) • Has continued to the present as landmasses and especially islands are first colonized by humans
Umbrella species
• A species that, when protected, also helps protect other species - Often large species that need large amounts of habitat - Often require relatively pristine habitats (e.g., oldgrowth forest) - Protecting their habitat automatically protects others • Primate example: many different primates!
4. Vocal Communication
• Advantage: ability to attract the receiver's attention without being in view • Anatomic specializations for long distance calling - Air sac or special bony pouch in some arboreal species
Socialization is important in primates
• Altricial state at birth • Long period of dependence • Slow maturation • Heavy reliance upon learning rather than instinct for survival
5. Ecotourism
• Another form of conservation oriented sustainable development • Generates economic revenue from land set aside for conservation • Fairly good track record, but unhealthy travelers pose risks to primates • Main problem: tourism is fickle--what happens when there are no tourists (e.g., during political instability)?
What do NHPs know about others' state of mind?
• Apes and some monkeys seem able to predict what others will do and modify behavior accordingly - Is this based on associative learning? - Or on knowledge of the mental states of others? - Difference is important: e.g. deception requires manipulating others' beliefs about the world
How intelligent are nonhuman primates?
• As social animals, what do they know about one another? • Do they understand third-party relationships? - Kinship relationships - Dominance hierarchies • Do they know others' thoughts and intentions? • Can they plan ahead ("mental time travel")?
What can you do?
• Awareness • Support conservation organizations • IUCN, World Wildlife Fund, Conservation International • Be a smart consumer: • Palm oil • Be a smart traveler: • Ecotourism where money goes to local community, local wildlife, conservation efforts • Research
"Aunting to death"
• Awkward (and occasionally fatal) infant handling by immature females • Is this an evolutionary strategy? • Proximate explanation: inexperienced females don't know how to take care of an infant • Ultimate explanation: removing future resource competitors • This may explain why low-ranking females are more wary of allowing their infants to be handled than high-ranking females (e.g. matrilineal baboon societies)
Socialization
• Behavior learned through observation of and interaction with others in the social group. • Begins very early on in life • Can occur when infants play and explore, or just through general interactions • New infants often draw attention from other group members
Sexual coercion (male)
• Behaviors by males toward females to increase the chance that the female will mate with him and not with other males when she is likely to be fertile • This comes at a cost to the female • Sexual coercion is more likely in species with high sexual dimorphism in
Growing quickly
• Benefits - Minimize time spent in highly vulnerable stage of life - Survival may depend on reaching adulthood quickly if environment is unpredictable or highly seasonal • Costs - Rapid growth requires a lot of energy
Growing slowly
• Benefits: - Slower growth means reduced food requirements - Minimizes risk of dying from starvation during juvenescence - Slow-growing juveniles sacrifice rapid growth to stay alive longer • Costs - Increased vulnerability to predators
2. Visual Communication: Body and tail postures
• Better for distance messages - Courtship - Dominance
2. Visual Communication: Coloration
• Better for distance messages - Species recognition - Signal quality or dominance status - Advertise reproductive state - Increase attractiveness to alloparents
1. Concentrate on areas with high biodiversity
• Biodiversity hotspots are areas that: - Contain high biodiversity - Are under threat • Specific criteria: - Must have at least 1,500 endemic plant species (0.5% of the world total) - Must have lost 70% of its habitat due to human activity • There are 36 hotspots identified worldwide - Cover 2.3% of Earth's surface - Support more than 50% of endemic plants - Support about 40% of endemic birds, mammals, reptiles, and amphibians • Conservation efforts in these areas can have a particularly large impact
Diversity of life
• Biodiversity: variety of life at all levels of organization - Genetic diversity: differences in DNA among individuals - Species diversity: the number or variety of species in a particular region - Ecosystem diversity: the number and variety of ecosystems, including different communities and habitats in an area
Why are primate brains so large brains?
• Brains are expensive tissues: - 2% of our body weight, 20% of our metabolic costs • Costly in other ways too - Influences life history traits such as reproductive age, interbirth interval, litter size - Life history theory: trade-offs • Natural selection is unlikely to favor such a costly organ unless it is adaptive
Hunting for the bushmeat trade
• Bushmeat trade: hunting wild animals to sell • Shift from small-scale subsistence hunting to large-scale hunting for profit • Causes local extinctions and threatens survival of many species • Volume of the bushmeat trade in West and Central Africa estimated at 1-5 million tons per year
Flagship species
• Charismatic species that can gather support from the public • Chosen for their vulnerability, attractiveness, and "charisma" • Useful in protecting many other species that share the same environment • Primate example: mountain gorilla
Ape Theory of Mind
• Chimpanzees understand the goals and intentions of others • Limited evidence that chimpanzees understand false beliefs (but see videos that follow) • Chimpanzees may not understand others in terms of a fully human-like belief-desire psychology - Others have mental representations of the world that drive their actions even when those do not correspond to reality
Apes have (at least partial) Theory of Mind
• Chimps take advantage of discrepancies between their own knowledge and that of others.
Latitudinal gradient has many causes
• Climate stability, high plant productivity, no glaciation • More niches, species coexistence • Diverse habitats increase species diversity and evenness • Ecotones (transitional area between biological communities)
Greater fecundity (reproductive rate) in provisioned colonies
• Compared to wild primate groups, females in captivity or in free-ranging colonies provisioned with high-quality food have: - Higher reproductive output - Shorter inter-birth interval - Younger age at first reproduction
Conservation Biology
• Conservation biology: the study of the factors behind biodiversity loss and approaches to protecting and restoring biodiversity • An applied and goal-oriented science • Conservation biologists integrate evolution, extinction, ecology, and environmental systems • Increasingly important in primatology
Any consensus with intelligence hypothesis?
• Data provide support for more than one hypothesis • Can have confounding variables (e.g. group size and home range are also correlated!) • There are exceptions: great apes live in "small" groups but have larger neocortex ratios than other primates, may use complex extractive foraging? • → It is likely that a combination of social and ecological factors drove the evolution of large brains in primates
Males as "hired guns" for females
• Defending their mates and home ranges • Males' active defense increases food supply and secures access to food resources • May also attract females in female dispersed species • By defending food and space, males are indirectly increasing their access to female mates
How do males know when female fertility peaks?
• Depending, females advertise the timing of ovulation or have concealed ovulation • Cues may be used (e.g., scent, "proceptive" behavior) • Size and coloration of sexual swelling • Coloration of swelling of areas around neck and throat
1. Scent marking
• Deposited on objects and/or dispersed in the air to: - Mark territories - Attract mates - Advertise dominance status - Communicate sexual receptivity - Mediate aggressive or competitive encounters • Most important in solitary, nocturnal primates (strepsirrhines), but also common in Callitrichidae
Intrinsic factors influencing species vulnerability
• Diet • Behavior • Geographic distribution • Population size • Social System • Body size • Pace of reproduction and life history
Species Distributions
• Different species have different spatial distributions • Endemism • Natural rarity
Spatial Distribution of Food
• Different types of foods vary in abundance over space • Food patches: discrete clumps of food resources - Single fruiting tree - Clusters of the same tree species with overlapping canopies
Infant mortality: Stochastic events
• Difficult to determine true impact of predation on infant mortality • Infants make easier prey • Some predators may be incapable of capturing an adult but able to take infants
Hunting
• Disproportionately affects large-bodied primates • Moderate hunting pressure can have large consequences
Age-graded groups (males)
• Dominant male allows a son to remain in the group or immigrant male to join • Dominant male benefits from having a coalitionary partner to help defend the group or the home range • Dominant male sires the majority of offspring
Infant mortality: Disease
• Ectoparasites, gastrointestinal parasite infections, Ebola, yellow fever, various unknown infectious diseases... • Chacma baboons: - 50% of all infant mortality was attributed to tick infestations in one population
4. Community-based conservation
• Efforts to preserve local wildlife initiated by the community itself • Revenue (usually from ecotourism) is shared by the community • Allow more financial benefits to reach local people so they get real value from conservation • Main problem: corruption • Also: often focus on few charismatic species while others continue to be hunted/overexploited
Why does hunting continue? It pays to break the law
• Enforcement and prosecution are rare for illegal logging and poaching - In Brazil, loggers make $75 US per tree, but face a fine of only $6.44 - In Mexico, poachers make a net average $191.57 per trip, but face a fine of only $5.66 • Bushmeat hunting is a primary source of income for millions of people with no alternatives available
Male dispersal strategies in polygynous groups
• Enter alone, take over group, and oust the previous resident male • Or, may cooperate to take over the group and oust the previous resident male - If so, the dominant will then evict the others after successful takeover - Unstable multi-male groups
Extrinsic threats to primates: non-anthropogenic
• Environmental stochasticity (i.e., randomness) • Demographic stochasticity (sampling variation in births and deaths) - May lead to unbalanced age-sex classes
Aging
• Experience of old animals depends on the social organization of the group/species, and the reproductive history of the individual • Old animals generally rest more and feed less • Old animals may also move differently (walking on ground rather than leaping across gaps in trees) • Some old animals are more socially isolated (especially in the dispersing sex)
Primates understand third-party dominance
• Experiment 2: Simulated rank reversals in baboons • Playback experiments with "dominant grunts" and "subordinate barks" • Play these in unexpected sequence (dominance rank reversals) • E.g., if ranks are A > B > C > D • Play C grunt followed by B bark • Other females are more attentive to simulated reversals than to expected sequences • Implies knowledge of the relative ranks other members in their groups
Biological Extinction
• Extinction is a fundamental part of the evolutionary process--almost all species that have ever lived are now extinct • Therefore, extinction is not intrinsically a bad thing • It is the current rate of extinctions that is concerning
Form strong relationships with other females
• Female coalitions may protect infants against: - Predators - Male infanticide, particularly if small sexual size dimorphism - Female harassment • Females may form strong relationships with females to increase likelihood of gaining coalitionary support
Females are not always free to choose
• Female mate choice is a behavioral pattern that leads to a female being more likely to mate with certain individuals • Female mate choice is constrained by male strategies - Male-male competition may prevent a female from mating with her preferred partner if he is low-ranking - Male sexual coercion (male aggression to female) may prevent a female from choosing a different male • The observed behavior may not always reflect a female's preference
Sex differences in diet
• Female primates generally have higher quality diets than males, especially in sexually dimorphic species • Smaller body size • Reproductive effort: females > males • Food is more limiting for females
Male vs. female lifespans
• Female primates live longer than males • Males tend to have riskier lives - Dispersal - Higher intra-sexual competition - More physical fighting • For example, in chimpanzees: - 41% of females survive to 15 years of age - 27% of males survive to 15 years of age
How do females show mate choice?
• Females can show pre-copulatory mate choice - Direct or indirect mate choice before mating • Females can show post-copulatory mate choice - Cryptic (not observable) mate choice that occurs after mating
Exchanging services with females (males)
• Females do not always prefer to mate with the highest ranking male • In exchange for copulations, males may: - Groom females - Protect their infants - Share meat with females
3. Fires
• Fires set by farmers often spread out of control, especially in dry forests • Most fires today are directly or indirectly due to humans • Can alter forest structure and composition, increase the risk of invasion of alien species, and threaten biodiversity
Organisms and need for energy
• Food (calories) are essential for growth, survival and reproduction • Total energy required depends on four components: - Basal metabolism - Active metabolism - Growth and growth rate - Reproductive effort
Foraging Behavior
• Foraging: searching for, handling, and eating foods • Primates may spend >50% of all waking hours foraging • Foraging strategies differ among individuals, populations, and species
Measuring cognitive complexity
• Forebrain shows greatest diversity in size and folding • Neurons concentrated in outer layer: "cerebral cortex" • Mammalian neocortex covers almost entire forebrain • Neocortex ratio: neocortex volume/volume of the rest of the brain
Primate Foods
• Fruit • Leaves • Insects • Also - Seeds - Grasses, tubers, corms (enlarged stems) - Gum - Vertebrates (birds, frogs, bats, other primates) - Non-insect invertebrates (clams, snails, scorpions) - Bark, fungus, soil (often for traces minerals) • Water (directly or through food items)
2. Ecological Factors: General Problem Solving
• Generalized abilities for innovation and behavioral flexibility may lead to more efficient foraging • New food resources may become accessible by inventing appropriate solutions to novel problems • Acquiring new food processing techniques by observing and learning from others • This could be useful for both ecological and social challenges • Key prediction: brain size is positively correlated with frequency of novel solutions to problems and social learning
The lives of juveniles: finding food
• Generally forage less efficiently than adults • May be able to exploit resources that adults can't • Diet during juvenescence may have critical implications for later life
5. Climate change
• Global average temperature has risen rapidly over the last century • Caused by increasing greenhouse gases produced by human activities • Climate change will lead to altered weather patterns • Loss of entire ecosystems, inability to move home ranges as environment changes will lead to extinctions
Grandmother hypothesis
• Grandmothers who help raise/ provision their grandchildren increase their daughter's fertility - Shorten inter-birth interval - Provisioning helps grandchildren gain weight • Menopause is directly adaptive via increases in the production or survivorship of descendants • Women stop reproducing because, at some point, there are greater fitness benefits to be had by helping daughters and grandkids than by having more babies
1. Social factors that favor large brains: Group Living
• Group living leads to: - Competition over food, mates, grooming partners - Differentiated social bonds among group members • As social complexity increases, so do the cognitive demands of keeping track of relationships, maintaining social bonds, etc.
Habitat disturbance
• Habitat destruction: deforestation without regrowth • Habitat fragmentation: continuous habitat chopped into small pieces • Habitat degradation: a gradual reduction of habitat quality
Spatial Distribution of Food Patches: Clumped
• High-quality foods • Clumped/patchy distribution • Monopolizable (worth competing over) • Induces contest competition • Example: fruit
Food distribution influences range size
• Home range area and day range length depend on diet
Evaluating the different hypotheses regarding intelligence
• How do we measure intelligence? • Primates don't fill out IQ tests, so we need a proxy for cognitive complexity • Brain divided into three portions: - Hindbrain controls basic functions like breathing, coordination - Midbrain processes sensory input - Forebrain is large and divided into hemispheres and lobes; it controls higher cognitive functions
4. Mechanism
• How does the signal affect the receiver? - Is receiver responding to information "encoded" in signal (symbolic meaning)? - Does the receiver associate the call with a particular event in time (natural meaning)? - Is receiver responding to some physical quality of the signal? - Is receiver responding to who is signaling?
Causes of the 6th mass extinction
• Human activities • Habitat loss • Over-exploitation • Invasive species • Pollution • Global climate change
Hunting for subsistence
• Human foraging societies have hunted primates as a source of food for thousands of years • Traditionally involves inefficient weapons (e.g., poison-tipped blow darts) • Relatively small impact
3. Concentrate on the most vulnerable species
• IUCN Red List: an inventory of the conservation status of different species • Species are assigned a conservation status based on: - Rate of decline - Population size - Area of geographic distribution - Degree of population and distribution fragmentation
Habitat loss in Borneo
• Illegal logging, fires, climate change, and clearing for palm oil plantations • Bornean orangutans have suffered ~25% reduction in suitable habitat since 1950s • By 2080, they are projected to lose up to 75% of suitable habitat that remains today • Habitat loss is a major threat to orangutans, both in Borneo and in nearby Sumatra
Exploitative male-infant relationships
• In baboons and geladas, an adult male will often pick up and carry an infant when he is involved in a conflict with another male • This puts the infant at great risk! • Agonistic buffering hypothesis: having an infant may help diffuse aggression by making the other male reluctant to attack because females may join in if an infant is at risk • Parental care hypothesis (doubtful): male may be trying to protect the infant from the other male during a conflict
Male-female affiliative and cooperative relationships
• In female-dispersed groups, males sometimes form strong affiliative (i.e., friendly) relationships with females • In pair bonded groups, males usually form strong affiliative relationships with females and/or infants • Males may cooperate with females in grooming, protection, infant tolerance/care • Females may otherwise disperse to another male
Male mate choice
• In general, mate choice is not as important for males as for females, but... • ... mating and mate guarding can be costly for males - Guarding a female means lost opportunities with other females - Males may not be physiologically able to mate with all estrus females • Therefore, males may sometimes show mate preferences • Males may prefer mating with females with higher fertility - High-ranking rather than low-ranking females - Prime-aged females that have already successfully reproduced rather than young, inexperienced females - Females who are in the ovulatory phase of the reproductive cycle
Primate Life Histories
• In general, primates have long life histories • For their body sizes, primates have live a long time and reach sexual maturity late • But there is variation within primates - Strepsirrhines: relatively fast life history compared to haplorrhines - Monkeys: slower life history than strepsirrhines but faster life history than apes - Apes: very slow life history
Positive male-infant relationships
• In most polygynous species, males form weak relationships with infants, might occasionally play with them or groom them • In pair bonded species, males may form strong relationships with infants characterized by frequent grooming, carrying, and food sharing with infants • In most species, males defend infants from infanticidal males
Cryptic female mate choice
• In some animals, females may control which male fertilizes her egg by mating promiscuously and exerting cryptic choice: - Discard or destroy sperm of particular males - Allow/impede ovulation - Adjust preparation of uterus before embryo implantation • It is unclear whether and to what extent these mechanisms occur in primates (indirect evidence only) • E.g. Bruce effect: selectively aborting • Females may also affect the likelihood that her infant will survive after birth -Invest more or less in the offspring • Mac also had allow or impede infanticide but I wonder if any females willingly let their infants be killed! Perhaps ask her or check book.=
Mast fruiting
• In some forests, many trees may flower and fruit in synchrony • Mast fruiting: synchronous variable production of large fruit crops ('masts') among years of smaller crops • This strategy makes it impossible for animals to eat all of their fruits
Policing (males)
• In some species with female dispersal, males police interactions between females • Male will intervene during femalefemale conflicts and decide the outcome • Can lead to more egalitarian female dominance relationships • Might reduce the risk of dispersal by low-ranking females (keeps higherranking females from excessive domination of lower-ranking females)
Education programs
• Increase public awareness, both local and international • Stimulate research • Training for future conservationists
Communal infant care
• Infant handling includes grooming, carrying, and nursing other female's offspring - Reduces traveling costs for mother - Allows mother to forage more efficiently without having an attached infant - Reduces female inter-birth interval - Increases chances of adoption and infant survival if mother dies
Disease
• Infectious diseases can decimate primate populations • Disease transmission is exacerbated due to primate sociality • Human disturbance of ecosystems and climate change may increase the spread of infectious disease
1. Social factors that favor large brains: Intelligence
• Intelligence could be socially advantageous: - Form and keep track of coalitions, alliances, and dominance hierarchies - Reconcile disputes - Deceive others and detect deception - Engage in reciprocity - Keep track of own and other's relationships
2. Motivation
• Internal state of the actor - Emotions - Intentions • Association between signal and motivation is not always conscious
What selection pressures favored intelligence in primates?
• Large brains and cognitive skills are linked to innovation and behavioral flexibility - The ability to invent solutions to novel problems - The ability to learn new behaviors from others • Two main evolutionary pathways may have produced this: - Social factors associated with living in large complex social groups - Ecological factors associated with locating and processing food items
Primate Research
• Learning about primates' biological requirements will help us design management policies • Surveys allow us to estimate population density and distribution • Feeding and ranging data reveal dietary and habitat requirements • DNA can be obtained from hair and feces to investigate gene flow and population viability
Why take care of someone else's infant?
• Learning to mother hypothesis - Benefits alloparent (often juvenile females) - Individual selection • Mother relief hypothesis - Benefits mother - Kin selection & inclusive fitness • Both benefit if the alloparent is kin
Primate lifespans
• Lifespan and body size correlated - larger bodied animals (including primates) live longer - Monkeys live 15 - 30 years - Great apes live up to 50 years - Humans can live up to 120 years
Biodiversity is unevenly distributed
• Living things are not distributed evenly on Earth • Latitudinal gradient: species richness increases toward the equator • Example: Canada has 30-100 species of breeding birds, while Costa Rica has more than 600 species • The tropics contain most of the earth's biodiversity including most primates
Spatial Distribution of Food Patches: Even
• Low-quality foods • Evenly distributed • Not monopolizable (or not worth trying) • Induces scramble competition • Examples: leaves, grass
Knowledge of others' thoughts and intentions
• Machiavellian intelligence: Form of intelligence involving tactical deception - Individuals perceive the world through their own and other's perspectives - Adjust behavior accordingly to advance their own interests • Knowledge that others don't necessarily see what you see, or know what you know • Awareness of this discrepancy allows informed individuals to manipulate others to their advantage • The ability to deceive would indicate the presence of theory of mind • Lots of anecdotal evidence for "tricky" behavior in primates - Sneaky copulations - Fake reconciliations - False predator alarm calls • Is this deception, or is there a simpler explanation?
Male dominance relationships
• Male contest competition can be intense and lethal • Therefore, males often form dominance relationships
Sperm competition
• Male-male competition can still occur after copulation when females mate promiscuously via sperm competition • Sperm competition and cryptic female mate choice likely play important roles in species where males experience scramble competition for access to females
Male dispersal strategies in polygynandrous groups
• Males can enter alone or with other males 1. Takeover and oust the previous resident male(s) 2. Take over the dominant position while the previous resident male(s) stays in group as low-ranking 3. Peacefully enter as a low-ranking male • Prime-aged males are more likely to enter aggressively and try to gain high dominance rank than younger males • A male may not be able to monopolize reproductive opportunities but is less vulnerable to take overs
Male dispersal strategies in solitary species
• Males try to establish a large home range • Can monitor the reproductive status of several females • E.g. Orangutans
2. Ecological Factors: Protected Foods
• Many primates rely on protected foods that require complex processing techniques to extract the edible parts - Examples: shelled nuts, mollusks, ants/termites, roots/tubers • Extracted foods tend to be very valuable: rich in proteins and fats
Multimodal signals
• Many signals used by primates probably use more than one mode of communication at the same time • Example: Vocalizations and facial expressions are often combined • When used together, signals can: - Reinforce - Enhance - Create a new message
Temporal Availability of Food
• Many tropical forests show strong seasonality - Usually "rainy season" vs. "dry season" • This typically has strong effects on which foods are available
There have been at least 5 mass extinction events
• Mass extinction event: widespread and rapid decrease in life on earth (both abundance and diversity) • Determined from abrupt changes in species represented in the fossil record • Mass extinctions are often followed by evolutionary diversification of surviving species (i.e., recovery) and appearance of new taxonomic groups
Transitioning to adulthood
• More gradual for males than females • Dispersal usually takes place before puberty or before dispersing individual becomes sexually active • May be difficult time due to new demands of reproduction • High mortality in dispersing sex
Sex differences in weaning
• Mothers might be expected to wean one sex later than others if the extra investment translates into higher maternal inclusive fitness • Example: High-ranking chimpanzees females invest more in sons than in daughters, weaning sons later
Conservation status of primates
• Nearly half of all primate species in the wild are threatened by extinction • Some of the most threatened primates are - Golden headed langur - Black-crested gibbons - Northern sportive lemur • Why are some primates but not others threatened by extinction? What determines a species' vulnerability? - Intrinsic factors--biological features of the animals themselves--make some primates more vulnerable - Extrinsic factors that increase extinction risk may be more or less severe in different areas
3. Integrated conservation & development projects
• Objective: to reduce external threats on parks by promoting sustainable development in surrounding areas • Based on idea that human pressures will decrease if people have better livelihoods • Assumes that if people are given stewardship over their natural resources, they won't over-use them • Usually implemented by external parties
1. Signal
• Observable action: the form that the act of communication takes - Examples: - Vocalizations (e.g., howling) - Bright coloration - Facial expressions - Scent-marking • A signal may be innate • But appropriate use must be learned in a social context - When to use it - How to respond to it
The Obstetrical Dilemma in Humans
• Obstetrical dilemma: humans have very large brains but also have a narrow birth canal (due to bipedalism) • This makes labor and delivery very difficult • Very early birth (altricial infants) • Skull plate fusion • Flexible pelvis • Assisted birth ("obligate midwifery)
Natural rarity
• Occurring at low numbers - Possible causes: small ranges, low abundances, and narrow habitat requirements - In most communities, a few species are very abundant and most are rare
3. Tactile Communication
• Occurs in intense and intimate social interactions - Mothers pacify infant - Reinforce bonds with allies - Female-male consortship - Reduce tension between adversaries • Can take many different forms - Touching - Grooming - Eye poking
4 Modes of Communication
• Olfactory • Visual • Tactile • Auditory
Defending the group (males)
• Once in a group, males may need to actively: - Defend the females from other males and predators - Defend the home range • Males often spend more time vigilant than females do
Priority-of-access (POA) model
• POA model: male reproductive success depends on both male rank and female reproductive synchrony • Can monopolize females when females come into estrus one at a time • Cannot monopolize access to all females when multiple females are in estrus at the same time • Importance of achieving high dominance rank
2. Visual Communication: Facial expressions
• Permit diverse messages • But only good for close-range • Often used for coordinating social interactions • Many are universal across species (yawn threat, grimace) • More limited in strepsirhines - Limited mobility of upper lip - Less nerves going to the facial muscles
Keystone species
• Plays a crucial role in the ecosystem • Has a disproportionate effect on its environment relative to its abundance • Examples: predators, prolific mutualists, ecosystem engineers • Primate example: gibbons can be critical seed dispersers
Low-quality diet
• Poor in energy and protein • Often high in cellulose, fibre, and secondary compounds like tannins and alkaloids • Also called a subsistence diet • Examples: Mature leaves, grasses
4. Pollution
• Primate habitats may contain natural resources (e.g., oil, gold, diamonds) that attract human exploitation • Habitat damaged by polluted air, water, and soils
Summary of primate intelligence
• Primate intelligence is thought to have evolved in response to social factors (complex groups) and/or ecological factors (planning and remembering fruit patches, extracting food) • Primates understand third party relationships • Some primates have theory of mind and may have the ability to use Machiavellian intelligence • Some primates are capable of mental time travel • Nonhuman primates do not have the same degree of social intelligence as humans do, but some have a faster working memory than humans
Food distribution and ranging behavior
• Primates need to travel to find their food • The distance traveled and total area used will depend on the density of the food they're after
2. Ecological Factors: Frugivory
• Primates, especially frugivores, need to integrate many sources of information to forage efficiently: - Spatial pattern - Phenological cycles (e.g., "will there be ripe fruit there today?") - Toxicity - Nutritional content • Good spatial memory would be useful because of the patchy distribution of fruit in time and space - Formation of mental maps - Larger home ranges • Key prediction: brain size is positively correlated with percentage of fruit in diet or home range size
1. Protected areas
• Protected area (PA): an area given some kind of official protection through laws or other effective means in order to conserve the ecosystem • PAs often in much better condition than neighboring lands in terms of land clearing, logging, hunting, grazing, and burning • PA creation strategies controversial: - Create new parks or strengthen the integrity of existing parks? - Protect most critically threatened ecosystems (which may fail), or take a triage approach--focus healthy ecosystems most likely to succeed in the long term? - The SLOSS dilemma: which is better to protect species: a Single Large Or Several Small reserves?
2. Ecological Factors for Intelligence
• Reliance on certain kinds of foods and foraging strategies could have high cognitive demands • Ecological intelligence hypotheses: cognitive evolution in primates was driven by foraging challenges
Menopause
• Reproductive cessation while other organ systems remain healthy • Human females experience decline in fertility in 30s, and typically lose ability to reproduce by age 50 • Among nonhuman primates, this may be unique to humans • Chimps: only 7% of wild chimps reach age 40, but tend to remain fertile until death • Menopause is present in other some other mammals (e.g., killer whales)
Monkeys have basic theory of mind
• Rhesus macaques choose to "steal" food from competitor that is: • Facing away from them (Exp. 1) • Facing away from food (Exp. 2) • Implies that they know what others see • Also choose food from box without a bell attached if competitor is facing away (Exp. 3) • Implies that they know what others hear • Use other's knowledge to their gain
High-quality diet
• Rich in easily digestible energy and protein • Also called a growth diet • Examples: Ripe fruits, flowers, seeds, young leaves, insects, vertebrates
What not to eat
• Secondary compounds: chemicals produced by plants that do not function in normal growth, development, or reproduction • They are chemical defenses against herbivores (usually taste bitter) - Alkaloids: can disrupt normal cell processes - Tannins: reduce digestibility of plants • Highest in mature leaves and seeds; lower in fruits, flowers, and new leaves
4. Conservation triage
• Should we give up on lost causes to maximize gains? If so, what exactly should we maximize? • Example: California Condor • Total of of 22 birds in 1987 • Huge long-term conservation effort: capture, captive breeding, reintroduction, monitoring • It has cost >$35 million to rescue the California condor from extinction • How many other species could this have saved?
Example of 4 components of communication: alarm call
• Signal: a short bark ("alarm call") • Motivation: caller is afraid or startled • Function: - Kin-based altruism (i.e., increase caller's inclusive fitness by alerting kin to dangerous predator)? - Scare off or confuse predator? • Mechanism: - Information transfer ("HAWK!!!!")? - Grab the attention of kin and hope they follow?
Example of 4 components of communication: infant screams
• Signal: an infant screams • Motivation: the infant is hungry • Function: the infant gets food (direct fitness benefit) • Mechanism: - Is the sound of a baby screaming attractive and makes a receiver want to take care of it? - Does a baby scream actually mean "please feed me?" - Is a baby's scream so annoying that receiver will do anything to pacify the baby?
Infancy in non-human primates
• Single, generally unassisted births - Exceptions: Callitrichids, humans • Grasping hands • When infants aren't parked, they are carried 24-7 - Continuous opportunity to learn through observation & experience
2. Agriculture
• Slash-and-burn agriculture: - Farmers burn vegetation to release nutrients necessary for growing plants on poor tropical soils - Rain washes away the nutrients - Soil can no longer support crops after a few years - Farmers move on and clear new areas to plant on
The lives of juveniles: acquiring social skills
• Social relationships are established through play • Play partners may become allies as adults
2. Sustainable use of natural resources
• Some argue that PAs in very poor countries are not viable or ethical • Parks should be opened up for "sustainable use" • Sustainable forest development: using the forest or forest products (e.g., harvesting trees, hunting) without damaging the habitat so that it remains biologically diverse and productive
"Attractive" plant parts
• Some plant parts are evolved to appear attractive to foraging animals such as primates • Evolutionarily speaking, the plant part "aims" to be eaten • These are reproductive parts
Hunting for other animal products
• Some primates are hunted for trophies, for body parts presumed to have medical properties, or for their beautiful coat • Trade for pets and scientific purposes • International trade has decreased substantially - Enforced regulations on trade - Captive breeding programs have reduced the trade for scientific purposes
Home ranges vs. territories
• Some species (e.g., gibbons) maintain exclusive home ranges - Home range = territory • Some species (e.g., marmosets) have overlapping home ranges and defend much smaller territories - Home range > territory • Some species (e.g., capuchins) do not defend specific areas at all (but can be xenophobic) - No territory • The occurrence of territoriality may depend on whether food resources are defendable
Primate adaptations to chemical deterrents
• Some species have evolved the capacity to detoxify certain chemical deterrents • Bamboo lemurs and cyanide • Charcoal ingestion by red colobus to detoxify secondary compounds • Geophagy: eating soil (usually claylike) • May neutralize certain toxic compounds in plant foods
2. Concentrate on important species
• Species categorized as one of the following may warrant particular conservation efforts - Keystone - Indicator - Flagship - Foundation
Indicator species
• Species whose presence indicates the health of the environment • Chosen for sensitivity to particular environmental condition • Early warning of environmental problems • Primate example: spider monkeys
Temporary entry to social groups (males)
• Strong breeding seasonality • There may be many extra-group males that invade during the breeding season • Difficult for the resident male to defend access to all estrus females • The resident male may still benefit from higher reproductive success than any individual extra-group male
Humans still outperform nonhuman primates...especially on social cognition tasks
• The "cultural intelligence" hypothesis • Multiple cognitive tests with 2-year olds, chimps, and orangutans - Cognition about physical world (e.g. tracking, using a tool) - Social cognition (learning to solve novel problems from observation or instruction) • Equal cognitive skills in the physical domain • Even small children outperform apes in the social domain
Theory of Mind
• The ability to attribute mental states (beliefs, intents, knowledge) to others and to understand that others' mental states may differ from one's own • Thinking about what another individual is thinking • Powerful basis for predicting actions
Mental time travel
• The ability to think and plan ahead • Consider future plans and consequences • Chimpanzees and orangutans can learn to delay immediate gratification (small fruit reward) to receive a larger reward in the future • Able to make choices in favor of future needs, even when these needs directly compete with an immediate reward. • Santino the chimp • Planned stone attacks on zoo visitors • Gathered piles of missiles for use later in the day • Also figured out that cracked rocks were easier to break apart to make more missiles
"Unattractive" plant parts
• The non-reproductive parts of a plant do not "aim" to be eaten (evolutionarily) • Physical deterrents - Physical attributes of the plant that make them unattractive to eat - Protective spines, hard shells and husks, stinging hairs • Chemical deterrents - Chemical attributes of the plant (secondary compounds) that make them difficult or dangerous to digest
Limiting factors for male reproductive success
• The only really important limiting factor for male reproductive success is access to mates • Why not food and safety?
Prioritizing conservation efforts
• The resources available for conservation (money, time, expertise, etc.) are limited • Therefore, it is necessary to develop priorities so that the available resources are used in a cost-effective way • Prioritization strategies: 1. Concentrate on areas with high biodiversity 2. Concentrate on strategic species 3. Concentrate on the most vulnerable species 4. Conservation triage: ignore "futile" cases to maximize species saved
Mapping on to females
• The spatial and temporal distribution of estrus females affects male strategies in a similar way to how food affects female strategies • Food quality and distribution determines female distribution • The distribution of fertile females determines male distribution - Social organization emerges from females mapping on to food and males mapping on to females
6th mass extinction: different from past events?
• This extinction event is unique because its causes are linked to human activity rather than natural events • It is believed that the extinction rate now occurring is greater than in past mass extinctions • At least 100 times higher than background rate • Can it be stopped or at least slowed?
Food in tropical forests
• Tropical forests may seem full of food, but they contain many species, and sometimes only a few trees of each type • Food availability varies in space and time • Can be patchy and unpredictable
Slow female reproductive rates
• Typical reproductive rates - Callithrichids: twins every other year - Monkeys: one every 2-4 years - Apes: one every 5-7 years • Each offspring is a large proportion of the female's total reproductive output • Each infant's survival is therefore very important!
1. Olfactory or Gustatory Communication
• Uses chemical signals (pheromones) - Airborne compounds stimulate nasal receptors (olfactory communication) - Waterborne compounds stimulate receptors on tongue (gustatory communication) • Probably the oldest form of communication • Main advantage: message persists after the sender has left • Cannot not be turned on/off
1. Logging
• Usually have a negative effects on primates • Can reduce food supply and increase population density • Low-intensity, selective logging can have a positive effects on some primates (e.g., Colobus) - Extirpation of predators - Can lead to increase of herbaceous plants eaten by folivores
Alloparenting or Infant handling
• Very young infants handled most • Subadult/nulliparous females handle most • Cases of affiliative infant handling and neglect/abuse
Parent-Offspring Conflict: Weaning
• Weaning is a major time for conflict • Offspring demand more from their mothers (& fathers) than they are willing to give
3. Function
• What does the signal do for the actor? • Adaptive value of the signal to the sender (and sometimes the receiver) • Either directly via increased actor fitness or indirectly via increased receiver fitness (kin selection) - Alarm calls function to warn kin - Threats function to defend food - Courtship gestures function to solicit copulation
Male Natal and secondary (breeding) dispersal
• Which group he enters at dispersal has consequences for his mating opportunities • Most attractive groups: - Contain unfamiliar and unrelated females - Contain male allies (parallel dispersal) - Have a more beneficial sex ratio - Will improve the male's dominance rank
Alloparenting ("Allo" = other)
• Who (besides mother & potential sire) cares for or interacts with infants? - Female kin - Juvenile females
Knowledge of third-party relationships
• Why would it be advantageous to understand third-party relationships? • It can be useful for evaluating possible coalition partners • Need to know about others relationships to know who will support you, and who will support your aggressor!